From Numbers- PETCO2 values- Capnometry

Clinical uses of capnography

Various factors result in either increased or decreased/absent PETCO2.

PETCO2 increased

output

Pulmonary perfusion

Alveolar Ventilation

Technical errors

Machine faults

Fever

Malignant hyperpyrexia

Sodium bicarbonate

Tourniquet release

Venous CO2 embolism

Increased cardiac output

Increased blood pressure

Hypoventilation

Bronchial intubation

Partial airway obstruction

Rebreathing

Exhausted CO2 absorber

Inadequate fresh gas flows

Leaks in breathing system

Faulty ventilator

Faulty valves

PETCO2 decreased

CO2 output

Pulmonary perfusion

Alveolar Ventilation

Technical errors

Machine faults

Hypothermia

Reduced cardiac output

Hypotension

Hypovolemia

Pulmonary embolism

Cardiac arrest

Hyperventilation

Apnea

Total airway obstruction

Partial airway obstruction

Accidental tracheal extubation

Circuit disconnection

Sampling tube leak

Malfunction of ventilator

The table above shows various factors that influence PETCO2 measurements at the lips. However, it is strongly recommended that capnometry be used always in conjunction with capnography as the latter, besides furnishing diagnostic and therapeutic information, is the only way to confirm the adequacy of CO2 sampling. Inadequate CO2 sampling leads to falsely low PETCO2 values which may be erroneously interpreted.